The Brachyceran family Vermileonidae (the sole family in the infraorder Vermileonomorpha) is a small family of uncertain affinities and unusual biology. It includes fewer than 80 described species, most of them rare and with restricted distribution, in 11 genera. Historically the vermileonids had been regarded as belonging to the family Rhagionidae,[13] possibly in a subfamily Vermileoninae. Their biology and morphology are so markedly distinct from the main Rhagionidae sensu stricto however, that the placement as a separate family has been widely accepted.[14]
The adults are slender, fragile, long-legged flies, vaguely reminiscent of small crane flies. The adults generally visit flowers for nectar, but adults of some species may not feed at all. The mouthparts of the adult are hypognathous, used mainly for extracting nectar from flowers, long, and straight. This might have something to do with the common name "snipe-fly" for the family Rhagionidae, but it would be misleading to use that name for Vermileonidae now, as they are no longer included in the Rhagionidae, which still are called snipe-flies.
Most vermileonid species are found in the drier regions of the western parts of Africa, from the Cape to Morocco, and also in the western parts of the Iberian Peninsula, mainly in Portugal.
Larvae
Pit traps of a larva of the wormlion Leptynoma sericea; the outline of the larva on its back under the sand is faintly visible, in contrast to most pit-digging antlions
The larvae of vermileonids are called wormlions which amounts to a direct translation of Vermileo. They have evolved the same elaborate mechanism for trapping prey, as one sees in many species of the Neuropteran family Myrmeleontidae, the so-called "antlions"; that is, they make cone-shaped pits in sandy areas and feed on insects that fall into the pits. The mechanism is elegant in that in both groups of insects, the larva creates the pit by flinging particles out. Much of the material falls back, coming to rest at effectively the critical angle of repose. This is a good example for convergent evolution.[15]
Thus, when a small insect, commonly an ant, blunders into the pit, its weight causes the sand to collapse below it, drawing the victim toward the center, where the larva lies in wait under a thin layer of loose sand. As soon as it is alerted by falling sand grains, the larva assists this process by vigorously flicking more sand out from the center of the pit. This undermines the pit walls and causes them to collapse toward the center. The sand that the larva now is flinging also pelts the prey with so much loose, rolling material as to prevent it from getting any foothold on the easier slopes that the initial collapse of the slope has presented. The combined effect is to bring the prey down to within grasp of the larva, which then can inject venom and digestive fluids.
Unlike the pit-digging Myrmeleontidae, vermileonid larvae do not travel round and round while digging the pit trap. Instead, they simply lie at the center with the rear end buried, and dig their heads repeatedly forward into the sand, flinging it out by vigorously straightening their fore ends. In contrast with conical digging, this approach is believed to take longer since more sand is likely to fall back into the pit when throwing from the center.[16] Finally, they cover themselves with a thin layer of sand while lying across the bottom of the cone. Wormlion larvae prefer shaded habitats over lit ones, fine sand of small particle size over coarser sand, and obstacle free soil.[17] All these factors enable them to construct large pits. Unfavorable conditions lead to more frequent relocation of the pits.[18]
The main enemies of the larvae of either antlions or wormlions are ground-hunting birds such as hoopoes and gallinaceous birds that learn to recognise their pits and probe or scratch them from the sand. If alarmed by such activity, the wormlion larva retracts abruptly into an S-shape under the sand, and if dug out, it retains that shape, not having much option for an alternative strategy at its disposal. Actually, because its skin is coated with sand, and it is very small, it is very easy to overlook while it lies still. However, if it is sufficiently teased after being dug out, it may begin to lash about powerfully, flinging itself away with enough force to escape its tormentor. It does not, however, hook its mouthparts into its hinder end to achieve an efficient leap such as some fruit fly and carrion fly larvae do.
The 10th and 11th segment of the larva each bears a transverse row of long hooklets that it uses in anchoring itself and in shifting sand. The fifth segment has a ventral pseudopod that helps to hold prey.[19] Not having sickle jaws like an antlion, the larva grasps prey by lashing forward and catching the victim by bending the head down to catch it between its two fang-like jaws and its pseudopod.
Like antlion larvae, vermileonid larvae are primarily found in sandy habitats, often semi-deserts, usually in the shelter of rocks or bushes, and they are voracious predators.
Classification
The infraorder Vermileonomorpha is often included within the Tabanomorpha, though the most recent classifications place them as its sister taxon.
The angle of repose, or critical angle of repose, of a granular material is the steepest angle of descent or dip relative to the horizontal plane on which the material can be piled without slumping. At this angle, the material on the slope face is on the verge of sliding. The angle of repose can range from 0° to 90°. The morphology of the material affects the angle of repose; smooth, rounded sand grains cannot be piled as steeply as can rough, interlocking sands. The angle of repose can also be affected by additions of solvents. If a small amount of water is able to bridge the gaps between particles, electrostatic attraction of the water to mineral surfaces increases the angle of repose, and related quantities such as the soil strength.
The antlions are a group of about 2,000 species of insect in the neuropteran family Myrmeleontidae. They are known for the predatory habits of their larvae, which mostly dig pits to trap passing ants or other prey. In North America, the larvae are sometimes referred to as doodlebugs because of the marks they leave in the sand. The adult insects are less well known due to their relatively short lifespans compared to the larvae. Adults, sometimes known as antlion lacewings, mostly fly at dusk or just after dark and may be mistakenly identified as dragonflies or damselflies.
Euroleon nostras is a species of antlion found over most of Europe. The scientific name can be translated as "our European [ant] lion". Adults resemble dragonflies or damselflies and may reach up to 30 mm (1.2 in) long, with a wingspan of 70 mm (2.8 in). The larvae prey on ants and other small creatures and require dry sandy soil in which to dig their pitfall traps.
The Asilidae are the robber fly family, also called assassin flies. They are powerfully built, bristly flies with a short, stout proboscis enclosing the sharp, sucking hypopharynx. The name "robber flies" reflects their expert predatory habits; they feed mainly or exclusively on other insects and, as a rule, they wait in ambush and catch their prey in flight.
The Therevidae are a family of flies of the superfamily Asiloidea commonly known as stiletto flies. The family contains about 1,600 described species worldwide, most diverse in arid and semiarid regions with sandy soils. The larvae are predators of insect larvae in soil.
The Brachyceran infraorder Tabanomorpha is a small group that consists primarily of two large families, the Tabanidae and Rhagionidae, and an assortment of very small affiliated families, most of which have been included within the Rhagionidae.
Chrysopilus is common, worldwide genus of predatory snipe flies. There are approximately 300 species in the genus, including fossil members that are sometimes found in amber.
Rhagionidae or snipe flies are a small family of flies. They get their name from the similarity of their often prominent proboscis that looks like the beak of a snipe.
Superfamily Tabanoidea are insects in the order Diptera.
Athericidae is a small family of flies known as water snipe flies or ibis flies. They used to be placed in the family Rhagionidae, but were removed by Stuckenberg in 1973. They are now known to be more closely related to Tabanidae. Species of Athericidae are found worldwide.
Arthroteles is a genus of snipe fly of the family Rhagionidae. Species of Arthroteles are moderately sized, from 5 to 7.5 mm. They are gray to dark gray in colour. Their antenna bears seven to eight tapering flagellomeres, the first much larger than all others.
Vermileo is a genus of wormlions in the family Vermileonidae.
Alhajarmyia is a genus of wormlion in the family Vermileonidae. It consists of two species from the Arabian Peninsula and East Africa. It is closely related to the Malagasy endemic Isalomyia.
Isalomyia is a genus of wormlion in the family Vermileonidae. It contains a single species Isalomyia irwini, endemic to Madagascar. It is closedly related to Alhajarmyia, a genus from the Arabian Peninsula and East Africa.
Namaquamyia is a genus of wormlion in the family Vermileonidae, containing a single species from Namaqualand, Namaquamyia manselli. The genus was first described by Brian Roy Stuckenberg in 2000, who originally named it Namamyia ; this name was preoccupied by the caddisfly genus NamamyiaBanks, 1905, so in 2002 Stuckenberg renamed the genus Namaqualandia.
Vermilynx is a genus of wormlion in the family Vermileonidae.
Vermiophis is a genus of wormlion in the family Vermileonidae.
Leptynoma is a genus of wormlions in the family Vermileonidae.
Lampromyia is a genus of wormlion in the family Vermileonidae.
Pachybates is a genus of flies in the family Athericidae.
↑ Stuckenberg, B.R. (2000). "Namamyia, a new genus of Vermileonidae (Diptera) from Namaqualand, with a conspectus of the Southern African genera and an account of their adaptations for anthophily". Annals of the Natal Museum. 41: 181–202.
↑ Hennig, W. (1967). "Die sogenannten "niederen Brachycera" im Baltischen Bernstein (Diptera: Fam. Xylophagidae, Xylomyidae, Rhagionidae,Tabanidae)". Stuttgarter Beiträge zur Naturkunde. 174: 51.
↑ Macquart, P. J. M. (1834). Histoire naturelle des insectes. Dipteres. Tome premiere. Paris: Roret. pp.578 + 8 pp., 12 pls.
↑ Katz, N.; Shavit, R.; Pruitt, J.N.; Scharf, I. "Group dynamics and relocation decisions of a trap-building predator are differentially affected by biotic and abiotic factors". Current Zoology.
↑ Richards, O.W. and Davies, R. G., Imms' General Textbook of Entomology, pub: Chapman & Hall, 10th ed 1977
Nagatomi, A. 1997. Family Vermileonidae. I: Papp, L. og Darvas, B. (red.): Contributions to a Manual of Palaearctic Diptera. 2: 447-458. Science Herald, Budapest.
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